The old "twice as loud" question

TheDarkLord

I have never had this question answered properly.  We all know that a 100 watt Marshall amp is not twice as loud as a 50 watt Marshall amp (the same for any other brand for that matter).  It will probably be cleaner for many of the lower to middle volume settings and it will probably be louder at full chat ..... but not twice as loud.

However, would two Marshall 50 watt amps, side-by-side, be twice as loud as one would?

Logic would tell me that would be more or less true - maybe not completely twice as loud, but getting there.

ICBM

A 70s Marshall Super Lead 100 is twice as loud as a DSL50...

Cirrus

All else being equal, 50w to 100w is a 3dB increase.

It doesn't matter if you swapped out the 50w amp for a 100w one or kept the first 50 watter there and added a second.

HOWEVER. In practice all else is never equal. More power into the same number of speakers makes them less efficient. If you add more speakers, they acoustically couple and give you more volume.

TheDarkLord

Cirrus said:

....... More power into the same number of speakers makes them less efficient .....

Let me be clear about that.   In the first scenario, you would have 1 x 50 watt head going though a single 4 x 10 cab.   In the second scenario, I would add another 1 x 50 watt head going through another 4 x 10 cab.  i.e.  double what was there before.  Will that give nearly twice as much volume?

I guess it would?

jellyroll

Instead of doubling the number of amps, why don't you halve the number of limbs on the drummer?

Phil_aka_Pip

jellyroll said:

Instead of doubling the number of amps, why don't you halve the number of limbs on the drummer?

Def Leppard tried that. I'm not sure it worked ...

ICBM

It will be substantially louder, but not twice as loud. How much "more loud" is "twice as loud" is a difficult thing to define because it depends on many factors. It used to be that 10dB more was considered 'twice as loud', in which case doubling the amps and speakers won't get you close to that, but in reality less than that can seem like twice as loud, possibly as little as about 6dB, particularly if that's from 3dB quieter than the rest of the mix to 3dB louder than the rest of the mix.

Double the amp power will give you an extra 3dB (whether that's two of the same amp or one amp of twice the power), and doubling the number of speakers will give you about an extra 2dB (depending on the speakers, the cabs and the room), so that's about 5dB in total. Not far off 6, but still less… and a *lot* less than 10.

And that's for steady-state measured power and decibels - perceived volume is much less accurate and can depend on dynamics, voicing and other things.

I was only slightly joking earlier. A 70s Super Lead 100 really is *very* loud compared to a modern 50-watter, far more so than you would expect from the difference in power rating - which the old amp comfortably exceeds anyway, and the new one doesn't. They're just far more dynamic and present.

chrisj1602

I found this once...

40 watts is 94% as loud as 50 watts.
30 watts is 86% as loud as 50 watts.
25 watts is 81% as loud as 50 watts.
22 watts is 78% as loud as 50 watts.
20 watts is 76% as loud as 50 watts.
18 watts is 74% as loud as 50 watts.
15 watts is 70% as loud as 50 watts.
12 watts is 65% as loud as 50 watts.
10 watts is 62% as loud as 50 watts.
9 watts is 60% as loud as 50 watts.
8 watts is 56% as loud as 50 watts.
7 watts is 55% as loud as 50 watts.
6 watts is 53% as loud as 50 watts.
5 watts is 50% as loud as 50 watts.
4 watts is 47% as loud as 50 watts.
3 watts is 43% as loud as 50 watts.
2 watts is 38% as loud as 50 watts.
1 watt is 31% as loud as 50 watts.

Found it here... http://www.amptone.com/g112.htm

Cacofonix

ICBM said:

A 70s Marshall Super Lead 100 is twice as loud as a DSL50...

...which itself is twice as loud as a jumbo jet at 3m from turbine centre.

I turned it to half way and found I couldn't hear it.

It took me three days for my hearing to come back.

ecc83

You have be careful to keep the same power going into the same speakers.

If you compare a 15W amp into a V30 to a 50W into the same speakers the latter will not be quite as loud as it might be because of thermal compression.

To do a scrupulously fair comparison you would need a bank of speakers of about 500W rating in total so that the amps never get close to compression any individual unit.

BUT! A big bank of speakers will have a very tight polar diagram so where do you stand to be deafened?

Dave.

TheDarkLord

There is a serious point to the question.

I am really a bassist (although I also play Teles through AC30s) and I play in a working band.  One of my many bass amps is the totally unbelievable AER Amp One bass amp.  A tiny combo which can hang with a rock drummer and loud ass guitarist.

It is total amazeballs on a number of fronts.  Size, features, volume per size ....... but the tones are increeeeeeedible. 

I'm not sure it has enough volume to use it in all scenarios though .... but very nearly.  So, I figured I'd get a second one and use two!  

Okay, I won't get quite twice the volume, but it should give me significantly more.  Church?

ICBM

If you do, be careful you don't cause uneven sound dispersion from the addition and cancellation of frequencies between the two amps. This can be more of a problem with bass, which is one reason PA systems often use a common sub bass cab rather than two.

You might need to experiment with separation and orientation of the two amps.

Reverend

ICBM said:

A 70s Marshall Super Lead 100 is twice as loud as a DSL50...

Nonsense.

No way would a modern Marshall be able to manage that.

hotpickups

Is that the 'out of phaseness' that people talk about when having two amps running etc

ICBM;410868" said:

If you do, be careful you don't cause uneven sound dispersion from the addition and cancellation of frequencies between the two amps. This can be more of a problem with bass, which is one reason PA systems often use a common sub bass cab rather than two.

You might need to experiment with separation and orientation of the two amps.

ICBM

hotpickups said:

Is that the 'out of phaseness' that people talk about when having two amps running etc

No, it's not as bad as that - two identical amps will always be in phase with each other (unless one has been modded or there's something like different channels being out of phase with each other), but you will still get some cancellation of frequencies at different distances and angles from the speakers... just less severe.

If your eyes can stand it, this is a sort of visual representation of what happens as the sound waves spread out from two speakers...

https://figures.boundless.com/11111/full/two-sources-interference.gif

The different colours represent different amounts of addition or cancellation. This is for one frequency too, it becomes almost impossibly complex with a mix of frequencies - but the end result is that the sound is not the same at different places in the room. You might need to try different separations or even have the amps pointing in different direction, or stacked on top of each other, to try to minimise it.

lespaulcustom68

Cacofonix said:

ICBM said:

A 70s Marshall Super Lead 100 is twice as loud as a DSL50...

...which itself is twice as loud as a jumbo jet at 3m from turbine centre.

I turned it to half way and found I couldn't hear it.

It took me three days for my hearing to come back.

How'd you balance it on the wing???

John_P

Rather than adding an extra amp you might think about using the sub out on your amp and linking to the AER sub12 or similar.

The other option, I would be looking at is running through the PA - if the amp is loud enough to keep up with a drummer, then for bigger gigs I assume the drums are mic'd and you could feed into the main PA rather than getting louder on stage.

ecc83

Things are even more complex than your mind bending diagram suggests ICBM!

That only show the original propagation, in practice those waves will strike a surface and come back and interfere with the new outgoing waves and this will produce complex, "standing wave" patterns.

Upshot of that is that NOBODY can get a perfect rendition of ALL frequencies!

Dave.

Cacofonix

lespaulcustom68 said:

Cacofonix said:

ICBM said:

A 70s Marshall Super Lead 100 is twice as loud as a DSL50...

...which itself is twice as loud as a jumbo jet at 3m from turbine centre.

I turned it to half way and found I couldn't hear it.

It took me three days for my hearing to come back.

How'd you balance it on the wing???

We were using it as a wheel chock.  Twice as durable as the nearest market alternative* but the ground staff kept complaining of bad backs, so we had to stop using them.





*In independent tests.

impmann

Reverend;413505" said:

ICBM said:

A 70s Marshall Super Lead 100 is twice as loud as a DSL50...





Nonsense.



No way would a modern Marshall be able to manage that.

It would have gone pop way before the time taken to measure the SPL...

Zodiac51

You don't need to be twice as loud, you just need to be 1 louder....